#include<iostream>
using namespace std;
int main()
{
	int m, n;
	cin >> m >> n;
	int sum = 0;
	if (m % 2 == 0)
	{
		m += 1;
	}
	if (n % 2 == 0)
	{
		n -= 1;
	}
	int num = (n - m) / 2 + 1;
	sum = num * (m + n) / 2;
	cout << sum;
	return 0;
}